DETROIT (AP) - Safety regulators in the U.S. are investigating whether to add more than 1 million General Motors midsize cars to a recall for brake light problems.

The National Highway Traffic Safety Administration says it's checking into complaints about the 2004 to 2011 Chevrolet Malibu and the 2007 to 2009 Saturn Aura. The safety agency says the brake lights may not come on when the pedal is pressed, while at other times the lights can illuminate for no reason.

In 2009, GM recalled about 8,000 Pontiac G6 midsize cars from the 2005 model year for the same problem. The government announced in February that it's investigating whether to add 550,000 G6s sold from 2005 to 2009.

Now the agency is investigating 97 complaints from Malibu and Aura owners about the same problems. The two cars share many of the same parts with the G6, but GM spokesmen were unsure Tuesday whether all three cars have the same brake lights.

The Detroit company sold more than 1.5 million Malibus and Auras from 2004 through 2011, according to Ward's AutoInfoBank, but it was unclear how many of them are included in the investigation.

No additional recalls have been issued beyond the 8,000 cars called in for repairs in 2009, although NHTSA says it opened the probe "to determine if the scope of the recall should be expanded or an adjustment in existing remedies is required."

NHTSA says if the brake lights don't illuminate, drivers behind the cars won't be warned and that could lead to a crash. A GM spokesman said Tuesday the company has no reports of crashes or injuries.

In the 2009 recall, GM traced the problem to corrosion in a wiring connector. Dealers were to fix it by putting a lubricant on the connector to prevent corrosion. The company sent dealers a service bulletin in October of 2010 detailing how to fix similar brake light problems in Malibus and Auras, NHTSA said.

Some of the owners who complained about G6 brake light problems also said the cruise control may not engage or will disengage unintentionally.

Owners who suspect brake light or cruise control problems should take their cars to any Chevrolet, Buick, Cadillac or GMC dealer. GM shut down the Pontiac and Saturn brands in 2010 as part of its massive restructuring.